Electric contact



Sept. 3, 1929. KAMULLER 1,726,913

ELECTRIC CONTACT Filed May 17, 1 926 2 Sheets-$11881', 1

AK o

Sept. 3, 1929'. K. MULLER 1,725,913

ELECTRIC CONTACT y Filed May 17, 19126 2 sheets-sheet 2 PatentedL Sept. 3, 1929.

UNITED STATES KARL MLLER, on ESSEN-oN-THEVfnUHR, GERMANY.

ELECTRIC CONTACT.

Application ledMay 17, 1926, Serial No.` 109,795, and in Germany May 18, 1925.

In connection with electrical starting devices, it is already known that good results may be obtained when the switch-blade is moved between spring contact pieces.` It 1s 5 known in this case to fasten the contact pieces to the free end of a flat spring inembe'r and thereby hold them so that they are swingable. Consequently the Contact pleces,l in adapting themselves to the movement oi:

1o the switch-blade, experience anangular ros tation, which makes it impossible for a uniform contact to be obtained over the whole surface and further a corresponding ynonuniform wear on the contact pieces `takes place. Finally, in consequence also of the movement oil theswitch-blade, a rotation of the 'contact pieces, though it may only be small, takes place in the direction of motion which also hinders the correct engagement between the contact surfaces and gives rise to premature wear.

The object of the present invention is to enable the contact`blade to makegood contact with its opposing metal contact pieces with `onlyia lsmall amount .of `wear and to ensure a good contact being made even if the contacts are not in exactly the correct position, relatively to the switch-blade.

'lhe invention consists essentially in that the springactuated contacts are movably held in a slide guide and therefore the flat contactV surface presented by them `in any one position remains substantially parallel to this surface when the contact is in an other position and can, under the action of the spring, lie freely with its whole surface against the switch-blade.

Two constructional embodiments of the in,- vention are illustrated by way of example inthe various figures of the drawings, in

which y Fig. yl is a front elevation of the iirst embodiment of a starter provided with the new contact pieces with the front wall of the starter cut away,

Fig. 2 is a vertical section on the line II-fll of Fig. l,

Fig. 3 shows a pair ofcontact pieces in accordance Vwith the invention, together with its guiding means, partly in plan and partly in section on the line A-A of Fig. 4, in about full size,

Fig. 4; is a view seen from the lower sid of Fig. 3,

Fig. .5 is a view seen from the upperside of Fig. 3,

'Fig.`6 is a viewf seen from the left-hand side of Fig. 3, and y Fig. 7 is a section Jon the line B--B of Fig..3, `1 y Fig. 8 is a side elevation of the' second embodiment" partly in section on the `line A-Aof Fig. 9,

Fig. 9 is afplan'partly in section on `the line 13k-Blof Fig. 8, i

Fig.` l() is a cross sectionon the line C-C of Fig. 8, and

Fig. l1 shows thezbase-plate of the guidemember in: plan. i i

Referring tok the drawings, the holder c of the ,contact pieces is substantially U- shaped in cross-section and lits parallel side walls j arevseparated by a centraly *slot 71, in order to allowthe contact blade to pass betweenfthem. The outer halt of each side wall is provided with a guide-slot b which is open on the outside. The contact pieces a are -f also-of U-shaped cross-section and are so proportioned thatzthe internal distance between the side Wallsof the holder c corresponds with the external distance between the side-walls `of Athe contact pieces. a.' The two contact pieces are inserted: in the U- opening'of thev holder c with their bridges facing one another and so that the external projections'ct1 with ,which the contact pieces are. provided engage in `the slots l), whereby the contactfpieces are4 guidedl in a straight line and are prevented by the rear edges of the slots b :from being `pushed beyond` the central plane of the holder." i.

A` spring d which. embraces i the contact pieces is inserted in a groove `01 provided in the bottom face of theV holder c'. 'This spring :passes around theholderc and engages in the openings of the two Contact pieces and lies with its ends against the in ner surfaces of the bridges of these contact pieces, so that v'both contact pieces are pressed towards I the central lplane of the holder. f y

The holders ofthe Ycontact 'pieces are fastened in 'series above or beside one another l to a plate o which is made of slate or other insulating material each by means vof a screw le and a connecting `bolt A small flexible connector g is connected to one `of the two projections a1 on each contact piece and its fork g1 engages under a clamping screw f on the holder c. Both the holder c and the contact pieces a are made of metal.

The resistances are connected `in known manner at the back of the insulating plate to the connecting bolts m.

The switch blades are chisel-shaped at both ends and are carried by a metal bridge f n. They are in electrical connection with each other. The metal bridge is held in an insulating holder B which is guided by means `^`of two parallel rods tand, in Lthe `embodiment illustrated in Figs. l-t, in the direction in which the blades which are vin line follow in succession. order to 'drive the 4.bridge and the vblades there is provided an endless chain g which is adjusted abackwards and forwards alternately by means of a hand-wheel .-70 through .suitable gearing. The whole is enclosed by .a `protective casing u which can easily ybe -opened andy from which the hand .wheel p projects.

On adjusting the chain the blades are moved inline between each pair of contactpieces. Since the contact pieces are `guided at right angles tothe path of the blade an equally :good contact is always-made, even if the contacts orthe blades .arenot exact- 1y in a straight :line and rhave'rbecome worn to a different extent. Fnrther., the degree of wear on :the vvsurfaces of thecontactipi'eces has .no eiiect onthe eectiven'ess 'of the cont-act. n 1 v` The individual lcontact pieces can easily be chan-ged since, for thispurpose it 4is only necessary to unscrewlthe corresponding screw 7 whereupon the contact-piece can be drawn out backwardsfrom its guideagainst the action of :the spring.

In the yembodiment illustrated in Figs. 8411 the fixed .guide-body consi-stsf'ot a substantially lH-'shaped plate 'c in the cut-out portions oit which ithezreduced lowerends of the twov guide blocks fc?, c2 engage and are fastened together therewith Sby means vof the two screws lc, ltov the plate 0 of insulating material. Each of the guide-blocksc1, c2 is .provided witha contact piece a which is substantially -infthe shape of a rectangular tubularmember andisaguided with its two side Apieces.I 032, as fon/the yonehand .on4 the corresponding block cjlor c2 and ion the other hand von the base-platee. ln the inside of the "block -clcr fc2fthere isv provided a spring-actuated pressure :bolt .im Ywhich tends to press the .one contact piece against the opposite contact piece, but its action is limited because -the rear `wall ,at ofthe :contact piece abuts against the wall of the block c1 or the rear head of the lpressure bolt y For the purpose of conducting the current a flexible connecting band 1?/ is connected'on the inside of therear wall m4 ofl the .contact piece and is led first downwards and then bent round outwardly and upwards. The band y terminates in a plate e which serves as a pole piece and is fastened by means of a screw j' and engages over the upper edge of the side pieces a?. as that it serves as a guide for the latter.

For the purpose ot removing a contact piece only the screw f need be released after which the whole contact Apiece togetherl with the connecting band jz/ can be lifted upwards. Conversely the replacement also of .a Vnew contact piece or the assembly of the Contact pieces is extremely simple since the screw f is easily accessible from the top or the front.` Consequently in this form of starter the contact pieces can be arranged very closely together and the complete starter may be constructed so as to be extremely compact.

In addition to being employed on starters the new Jforms ot contacts can of course also be employed-on other switches, tor example, en .simple breaking switches, circuit changing switches,,separating switches in which case the ymovement of the switch-blade instead of being rfrom one side of the contactpieces to the other is suitably from above down between the contact pieces. When using such a tor-m of construction as a switch it is advisable Jfor each :ofthe contact pieces to be provided with a horn-shaped extension t illustrated in dotted lines in Fig. '8:in order to exert a blowing action which extinguishes any arcs which may be formed.

yI clai-m y I l. In an electric switch, a rectilinearly movable switch iblade, a rectilinearly movable spring-pressed contact arranged on each side ot the line of movement ot' the blade, each vcontact hav-ing a pair of spaced side pieces anda bridge piececonnectingthe side pieces and Aforming `a contact plate, a 4guide foreach contact, the said contact plates Aet the `contactsfbeing arranfred opposite each other and in parallel relation to eachother and thesaid side pieces Aof the contacts being insliding engagement with the guides .so as to guide the contacts on straight lines toward vor from each other and so as yto maintainthe contact plates in parallel yrelationship, andmeans for slidably moving the switch blade between and across the contact plates of .the contacts Jfrom side to side of the contacts.

.2. In an electric switch, a rectilinearly movable switch blade, a rectilinearly-mov able springspressed contact arrangedon each side of the line of movement vof the switch blade, each contact being in the form of a rectangular loop and having a pair ot spaced llO side pieces and a bridge piece at each end connecting the side pieces, one of the bridge pieces of each contact forming a contact plate, a guide on each .contact and arranged in the space bounded thereby, the said contact plates of the contacts being arranged their said Contact plates in parallel relationopposite each other and in parallel relaton- Ship E0 GCll Other, and means OI Sldably ship to each other and the said side pieces off' moving the SWtoh blade between and ooSS l0 the contacts being :in sliding engagement with the eonteet Plates 0f the Contacte from, Side the guide members therebetween so as to to 31de ofthe Contactsgucle the contacts on straight lines toward In testimony whereof I efHX my Signature or from each other and so as to maintain KARL MLLER. 

